diff --cc src/pmc/context.pmc
index 6338227,6338227..4bb023e
--- a/src/pmc/context.pmc
+++ b/src/pmc/context.pmc
@@@ -102,6 -102,6 +102,10 @@@ Mark Context as alive
          for (i = 0; i < ctx->n_regs_used[REGNO_PMC]; ++i) {
              /* Original code from CTX_REG_PMC */
              obj = (PObj *)ctx->bp_ps.regs_p[-1L-(i)];
++            if (obj == (PObj*)0x01) {
++                obj = NULL;
++                ctx->bp_ps.regs_p[-1L-(i)] = NULL;
++            }
              if (obj)
                  Parrot_gc_mark_PObj_alive(interp, obj);
          }